Do they really want that, though, or do they simply get more excited by it? Let's take a more striking example: someone trying to avoid wallowing in a pit of despair and grief over a loved one dying. I feel like many such people would tell you they are actively wanting to and even trying to avoid triggers for such, but once they run into one it pulls at them and they start to fall down a rabbit hole where a few hours later they are staring at old photos, listening to depressing music, and sobbing their eyes out.
Now, imagine you have the job to recommend content for them. I feel like not only would a compassionate person know to avoid these triggers "for the user's own good" (which I would find way too paternalistic), even a really competent human (or a truly powerful AI) that was optimizing for "what this user wants" would avoid triggering content as the customer probably is even able to express this want verbally.
The issue, though, is that if you happen to ascertain (whether by active analysis or more passive experimentation) "omg every time I show them this thing they immediately drop everything else they are doing and spend three hours watching similar videos!!! this is amazing: I have found the best possible thing to show them!!!" and act on that despite it not being what the user wants you are just being evil.
And that's Google: the people at Google that work on this software are evil. Google employees seem to just be selfishly optimizing for "engagement" (to the extent to which they succeed... honestly they aren't even all that great at it, but they do much better than we would actually want ;P) and will just blindly show people stuff that they themselves might actively wish to avoid but can't help but get sucked into... so Google can make more ad money.
In the case of these conspiracy theories, I will contend most people want to be informed. They are momentarily skeptical of something, which makes them likely to get turned on easily by these videos, but then it is Google that radicalizes them by realizing "omg when I show them more videos of this form they just keep digging into the rabbit hole!!! SO MUCH AD MONEY" and "ugh when I show them videos from the other side they get turned off and maybe even drop the whole issue and go off to do something else more productive... that sucks! :/".
The engineers at Google have thereby built a system that, sure, "shows you what you want", but it shows you the most twisted, myopic, and even cruel version of what you want in the name of making them ad revenue over all other potential benefits to the user. Sure, sometimes this can be rationalized as showing the user something they legitimately found fun or interesting, and if you go into it with a careful mind and a wall of defenses it is possible to get what you need despite this perverted optimizer... but, I would hope we all can understand that it goes much deeper than that and that the negative effects are not ones that should be ignored in the name of making more money.